How to configure the infrastructure required to host a mail server

SUMMARY

Many home users and small companies use an ISP for
hosting mail infrastructure, and in-source their mail server. To effectively host a
mail server, ensure that a permanent connection to the Internet is available. This article
describes how companies can migrate messaging infrastructure into their
organisation.

DETAIL

STEP 1: GETTING CONNECTED

The first step in publishing a mail server is
to configure a Windows NT/2000/2003 server that can be accessed from the
Internet. There are a variety ways to connect the server to the Internet, the common ones are
outlined below:

Dual Network Card Configuration
The simplest approach is to ensure the server has
two network cards. One of these cards should be configured with the IP
Addressing scheme of the Internal network. The other network card should be configured
to access the Internet using the settings supplied by your ISP. On this server,
either run a Proxy Server or enable Internet Connection Sharing (if using
Windows 2000). This will provide a basic firewall between the internal
network and the Internet.

Cable Router Configuration
Many home users and small companies use a Cable,
DSL or ISDN router/hub to provide Ethernet access to the
Internet. This provides the same functionality as the option outlined above,
except the hardware, software and maintenance costs are reduced. These
devices cost around $150 (USD). Such devices provide Address Translation and
can therefore function as a Proxy Server. Since these devices only expose
an external IP Address, the Network/Port Translation on the device will need
to be configured to allow Internet traffic on ports 110, 25, 80 and 8080 to
translate to the internal address of the mail/web server.

Enterprise
Configuration Larger
companies often interface to the Internet through a router of some description.
This router provides Ethernet access to the Internet (the router is normally supplied
and configured by your ISP). Most routers have an inbuilt Ethernet switch
that will allow the server to be placed on the Internet (assuming that an appropriate
public IP Address has been configured for the server). The simplest approach in this
situation is to place the mail server directly onto the Internet and use
an alternate interface to provide connectivity to the private network. In
many cases, companies use a firewall with multiple translated interfaces to provide
what is called a DMZ (Demilitarized Zone). For more information
about configuring servers within a DMZ, consult the documentation supplied with this
device.

STEP 2: CONFIGURING
DNS

By now, the mail server
should be accessible through the Internet as well as internally. The next thing to do
is configure the DNS settings. In order for other mail servers and clients to be able to
send mail to your mail server, the appropriate published DNS records are required.
These records are used by other mail servers to locate your server when they
attempt to parse recipient addresses (i.e. the records allow a domain name to equate to an
IP Address). Exactly how DNS is configured depends largely on whether you are
hosting your own publicly accessible DNS server or whether a third party
(typically an ISP) is hosting your DNS for you.

Traditional DNS implementations require a fixed or static IP address allocated
to the public interface of the appliance (router/server) that is the first point
of connection to the Internet. If the server has a static IP address, it is
possible to register an MX and associated DNS record that resolves to the external
IP address of the router/server. If the server does not have a static IP Address, the
domain will have to be registered with an ISP that provides Dynamic
DNS services (eg:www.dyndns.org). Dynamic DNS works by having an agent installed
on the public router/server interface that effectively notifies the
DNS Service provider of the IP Address. Most Internet Firewall Routers have this
capability built into their firmware. For more information on configuring Dynamic
DNS please refer to the documentation supplied by the DNS Service provider or
with the router.

STEP
3: CONFIGURING THE MAIL SERVER

Having
configured both Internet connectivity and publishing DNS settings to the
Internet. All that remains is to install the MailEnable server software. To do
this, download the installation kit
and run the installation wizard. The installation wizard prompts for the IP
addresses of the DNS provider. Use the settings published by your ISP (or if you are
hosting your own public DNS, use the local server's IP address). Once installed, run
the MailEnable Diagnostic Utility to ensure that the configuration is
correct.